The present invention relates to piston-type internal combustion engines, and is directed to improvements in or modifications to the engine described in my above-cited copending U.S. patent application Ser. No. 585,652.
My above-cited U.S. Patent Application describes an internal combustion engine including a cylinder, a piston displaceable therein, means including an intake valve for effecting the induction of a fuel-air mixture into the cylinder, and a control member (e.g., accelerator pedal) movable to control the engine output, the engine being characterized in that it includes a variable valve timing device controlling the timing of the intake valve, and a coupling between the movable control member and the variable timing device which coupling varies the timing of the intake valve in response to the movement of the control member to thereby control the quantity of the fuel-air mixture in the cylinder at the time of combustion. In the preferred embodiment of the invention therein described, the variable timing device effects a delay in the closing of the intake valve after the start of the compression stroke, the delay being increased when the control member is moved to lower the engine output, and being decreased or eliminated when the control member is moved to raise the engine output. Thus, the greater is the delay, the greater is the quantity of charge pumped back into the intake manifold during the early part of the compression stroke, the smaller is the quantity of charge in the combustion chamber during the combustion process, and therefore the lower is the engine output.
The engine described in the above-cited patent application further includes an arrangement for maintaining a substantially constant atmospheric pressure at the beginning of the actual compression stroke when the intake valve closes, and a substantially constant pressure at the end of the actual compression stroke, notwithstanding variations in the time of closing the intake valve. The engine thus maintains a substantially constant compression ratio in each cylinder and a substantially constant pressure during the combustion process under all load conditions, the pressure within the cylinder at the end of the expansion stroke decreasing with a decrease in load, thereby maximizing combustion.
A further embodiment of the invention is therein described wherein the arrangement for maintaining a substantially constant compression ratio in each cylinder, therein called a main cylinder, comprises an auxiliary cylinder for each main cylinder, and an auxiliary piston movable in each auxiliary cylinder, the inner ends of the two cylinders communicating with each other and defining a common combustion chamber with their respective pistons, the auxiliary piston being displaceable within its cylinder to increase or decrease the volume of the common chamber.
An important characteristic of the engine described in the above patent application is that the engine produces a relatively longer expansion stroke for partial (i.e., less than maximum) loads than the real compression stroke. Thus, the engine operates according to the ideal Otto cycle only for maximum load, and according to or close to the Atkinson cycle for partial loads. Such an engine may therefore be referred to as having an "Otto-Atkinson" cycle, and as shown in the above-cited patent application, it is capable of producing more complete expansion and exhaust, without pumping losses, and thus has better thermal efficiency than the conventional Ott-cycle engine for under maximum load conditions.